1. Technical field
This invention relates in general to alarm processing, and more particularly, to a diagnostic method for identifying from a set of generated alarms potential faulty components of a predetermined system; such as a power network, in real time.
2. Description of Prior Art
Alarm processing has been a traditional feature of Energy Managment Systems (EMS) and has remained basically unchanged over several generations of EMS designs. Problems with existing diagnostic methods are obvious, and operations personnel have consistently expressed the need for improved methodologies for monitoring the power system network. For example, identified state of the art processing drawbacks include: alarms which are not specific enough; alarms which are too specific; too many alarms occurring during a system disturbance; false alarms; multiplicity of alarms for the same event; and alarms changing too fast to be read on a display. These problems with existing technology are described further in an article entitled "Feasibility Study For An Energy Management System, Intelligent Alarm Processor" by B. F. Wollenberg, IEEE Transactions on Power Systems, Volume PWRS 1, No. 2, (May, 1986).
As a solution, the Wollenberg article proposes an expert system based on the concept that alarms should not be presented to the operator without interpretation. Instead, alarms are analyzed in a real time database of the EMS and only relevant alarms are presented to the operator. The suggested methodology for processing alarms is adjusted according to the state of the system. For example, during a thunderstorm certain alarms are automatically suppressed if they are expected to occur. From a review of the alarm rules and examples presented in the article, it appears that Wollenberg's expert system functions principally as an alarm filter that removes redundant alarms, rather than as a diagnostic system that identifies the faulty, or potentially faulty elements of the system. In addition, as presented, therein the described alarm processor is not, nor can it be interpolated to be, an operational expert system for real time application.
Another expert system for processing alarms in a power network is described in an article entitled, "An Expert System For Fault Section Estimation Using Information From Protective Relays and Circuit Breakers", by C. Fukui and J. Kawakami, IEEE Transactions On Power Delivery, Volume PWRD 1, No. 4 (October, 1986). This expert system estimates possible fault sections using information from protective relays and circuit breakers When a fault occurs, the system makes inferences based on knowledge about protective systems in general and information on the operating relays and tripped circuit breakers The article describes an example of fault estimation in a model network containing several substations, buses, transformers, and circuit breakers However, in a practical power network implementation, an extremely long time can be expected for fault detection using the backward chaining rule-based approach presented.
Another approach to fault diagnosis in a power network has been presented by Komai and Sakaguchi in an article entitled, "Artifical Intelligence Method For Power System Fault Diagnosis", released at the Second International Conference on Power System Monitoring and Control (1986). The Komai and Sakaguchi article descibes an approach different from the rule-based expert systems described above. Their motivation is to solve the problem of incompleteness of the knowledge base, which is an important limitation of present expert systems. According to the authors, expert systems will have the same ability to solve problems as human experts only when human expertise is fully encoded in the knowledge base. Although the approach is powerful in that solutions even under incompleteness and inconsistency of the knowledge base can be obtained, the system is slow. Thus, the approach described therein is inadequate for a real time application.
A review of the literature on available alarm processing techniques demonstrates the present deficiency in the art relating to real time processing of alarm signals in a power network. The present invention is directed to meeting this deficiency.